But why use a comma there when a semicolon accomplishes the same effect; it joins two complete sentences together with a slight pause shorter than a period might. And if all you want is a slight pause—for a parenthetical phrase or sentence fragment—the em dash does just nicely, and is not frowned upon.

We have conventions for a reason. We have an agreement on what works for everyone. Inventing your own meanings is great in the privacy of your own cube, but why invent something that already exists?